Brightener agent solutions



United States Patent O ""ce Patented Got. 15, 1968 3 406 118 This patent refers to isomeric agents in which metanilic BRHGHTENERAGENT SGLUTIONS acid is used in lieu of sulfanilic acid with the result that Christopher Tschal-ner, Warwick, and Richard such agents do not form stable solutions. According to Pichler, Cranston, R.I., assignors to Geigy Chemical the present invention, effective whitening agents may be Corporation, Greenburgh, N.Y., a corporation of 5 prepared from metanilic acid, and such agents form stable Delaware commercial solutions, using the special techniques and No Drawing. Filed Mar. 31, 1965, Ser. No. 444,435 materials as Set f th h r i ft 9 Claims- (CL 252-3012) It is one of the objects of this invention to produce highly eifective whitening agents. It is another object to ABS CT OF THE DISCLOSURE 1O prepare such agents which are relatively free from sodium chloride and similar deleterious by-products. It is a fur- Stable aqueous concentrates of an alkanolamine salt of ther object to produce whitening compositions which are 4,4-'- f -6-[bis(2 hydr XyethyDamistable aqueous solutions, even at temperatures of about -Y in ll n 0 C. It is yet another object to manufacture these fluoacid are prepared by converting the sodium salt thereof to rescent products by simple and economical methods. Other a partial acid salt by salting out with ammonium chloobjects will be apparent from the following description of ride, converting the acid salt to a free acid by the addithe invention. tion of hydrochloric acid, and then reacting the result- All of these objects are attained by preparing a stable ing free acid with an alkanolamine. aqueous solution of an alkanolamine salt of 4,4-bis-{4- [3-sulfoanilino 6 [bis(2-hydroxyethyl)amino]-1,3,5-

triazin-Z-yl]amino}-stilbene-2,2'-disulfonic acid which can This invention relates to the production of fluorescent be represented by the following structural formula:

I N N Q-HN-f IHN -OH=C HNH( \HNH 4X+ N N N N S03 S03- /1|\I (311: CH; (3112 \(IJHZ (1H3 CH2 (EH2 C|Hz 0H OH OH OH compounds particularly useful as agents for whitening tex- 40 wherein X is alkanolamine cation. These stable solutions tile fibers, paper and the like. It is more especially conare relatively free of NaCl (i.e., less than 6% of the cerned with the production of stable aqueous composiweight of the free acid or less than 1% of the brightener tions containing such agents. solution). Typical alkanolamines include the mono-, di- The operation of bleaching, or brightening, has been and triethanolamines; mono-, diand tributanolamines deconcerned for some time with the preparation of fabrics rived from l-butanol, Z-butanol, or 1 methyl-2-propanol; whose commercial value is dependent on the highest possi- N-methyldiethanolamines; N,N dimethylethanolamine; ble whiteness. Under the concept of bleaching, the texand N,N-diethylethanolamine. tile converters and paper manufacturers understand all In practice, the sodium salt of this sulfonic acid is first those upgrading procedures which are concerned with the prepared in aqueous solution, the sodium salt is converted removal of colored impurities or their conversion into to a partial acidsalt by salting out with ammonium chlocolorless substances. On the other hand, with optical ride, the precipitated acid-salt is converted to the acid by brighteners, an optical compensation for the yellow cast treatment with hydrochloric acid and the resultant acid is is involved. The yellow cast is produced by the absorpthen reacted with an alkanolamine, to give the desired tion of short-wavelength light (violet to blue). With opwhitening agent.

tical brighteners this lost light is replaced, in part, and H The following specific embodiments illustrate the inventhus a substantially complete white is attained. This addition without limitation to the details set forth. Parts and tional light is produced by the brightener by means of percentages, where mentioned, are by weight. fluorescence. Optical brightening agents (also referred to The sodium salt of the metanilic acid substituted stilas fluorescent bleaches or optical Whitening agents) bene-2,2-disulfonic acid referred to above may be preabsorb the ultra-violet portion of the daylight spectrum pared by any of the well-known suitable methods deinvisible to the eye, and convert the energy thus taken scribed in the prior art, e.g., those set forth in British up into the longer-wavelength visible portion of the spec- Patent No. 841,189 or Japanese patent of 1958, No. trum, i.e. into blue to blue-violet light. 7,638. An aqueous solution of the sodium salt is then In U.S. Patent 3,025,242, there is described a group of reacted with about 15-20 percent of ammonium chloride whitening agents derived from stilbene and sulianilic acid. to precipitate out the partial acid-salt as a slurry. During the addition of the NH Cl, the solution is kept below about 30 C. (about 25 C.) to prevent formation of insoluble gum and lumps. While maintaining the partially acidified slurry at less than about 30 C. (about 25 C.), hydrochloric acid is added until the slurry has a pH of about 2.0. The slurry of acid thus formed is then filtered. The filter-press cake containing about 30- 35% acid and about 7065% water, is reacted with diethanolamine to form the diethanolamine salt of the sulfonic acid in an aqueous solution containing about 15% of the salt brightener and boiling of the solution at 120-125 C. in order to remove the undesired ammonia. The solution thus prepared is relatively free of NaCl, containing less than 1% thereof. Such solutions are stable at about C. in that they exhibit no phase separation if the solution is frozen and then thawed at about 5 C.

If it be desired to free the acid substantially completely of sodium chloride, the filter-press cake may be Washed with an aqueous ammonium chloride solution. One of the outstanding characteristics of the acid crystals formed by HCl acidification as described herein, is that such crystals are of a form to be easily filtered and, if desired, washed. This acidification is carried at pH 4.0- 1.0 and preferably about pH 2.0. It has further been found that other acids, e.g., sulfuric, are not as successful for acid formation. Likewise, other ammonium salts, e.g., ammonium sulfate, are not as effective as ammonium chloride, to give end products which form stable aqueous concentrates. The salting out and acidification steps are preferably carried at a temperature of about C. but these temperatures may be varied without deleterious effects, from 0 to C. The soluble salt to be treated in the salting-out operation may be the potassium salt instead of the sodium salt and the same considerations with respect to the potassium chloride formed apply as in the case of the sodium chloride.

The alkanolamine salts in aqueous solution are sufiiciently stable for commercial use without further additions. In some instances, where the salt brightcner solutions may be subjected to unusual conditions of storage or when the wet acid cake was not washed substantially NaCl free, the brightener compositions may be modified by inclusion of special solvating and/or stabilizing agents. Dimethylformamide, in amounts up to 10% and preferably in amounts of 510%, is typical of such materials.

Other suitable changes and variations may be adopted where desired without departing from the spirit and scope of the invention as defined in the claims.

Cir

What is claimed is:

1. The process of producing a stable readily dilutable composition adapted for use as a brightening agent on cotton fibers, paper and the like, which comprises preparing an aqueous solution of an alkali metal salt of 4,4-bis{4-[3 sulfoanilino} 6 [bis(2 hydroxyethyl) amino]- 1,3,5-triazin 2 yl]amino} -stilbene-2,2'-disulfonic acid, while maintaining the solution below 30 C. adding ammonium chloride in an amount sufficient to precipitate out the partial acid-salt as a slurry, acidifying the slurry at about 30 C. to 0 C. by addition of hydrochloric acid to pH 4.0-1.0, filtering the slurry and reacting the wet filter-cake with an alkanolamine and boiling the mixture to produce an aqueous solution of about 15% of the alkanolamine salt of the disulfonic acid, said solution being relatively free of alkali metal chloride.

2. The process of claim 1 in which the filter'cake is washed with an ammonium chloride solution to remove substantially all occluded sodium chloride, before -reacting with the alkanolamine.

3. The process of claim 1 in which the alkanolamine salt reaction is conducted for a time and at a temperature sufficient to remove any ammonia formed in the solution.

4. The process of claim 1 in which the salting out with ammonium chloride and the acidification with hydrochloric acid are each carried out at a temperature of about 25 C.

5. The process of claim 1 in which the hydrochloric acid is added to pH 2.0.

6. The process of claim 1 in which the alkali metal salt of the disulfonic acid is the sodium salt.

7. The process of claim 1 in which the alkanolamine is diethanolamine.

8. The process of claim 1 in which the alkanolamine is monoethanolamine.

9. The process of claim 1 in which the hydrochloric acid acidification forms 4,4'-bis{4-(3-sulfoanilino) -6- [bis(2 hydroxyethyl)amino]-1,3,5-triazin-2-y1] amino} -stilbene -2,2-disulfonic acid.

References Cited UNITED STATES PATENTS 3,025,242 3/1962 Seylor. 3,211,665 10/1965 Allen et al. 3,239,513 3/1966 Hausermann.

HELEN M. MCCARTHY, Primary Examiner.

R. D. EDMONDS, Assistant Examiner. 

